WASHINGTON (AP) — Democrats fattened their majority control of the Senate on Tuesday, ousting Republican Sens. Elizabeth Dole of North Carolina and John Sununu of New Hampshire and capturing seats held by retiring GOP senators in Virginia, New Mexico and Colorado.

With 29 of 35 Senate races called, Democrats were guaranteed at least a 55-45 majority, including two holdover independents who vote with Democrats. But they were hoping for even greater gains in a political environment that clearly favored Democrats.

North Carolina state Sen. Kay Hagan, little known politically before her run, defeated Dole — a former Cabinet member in two Republican administrations and 2000 presidential hopeful. Dole had tried to tie Hagan, a former Presbyterian Sunday school teacher, to atheists in an ad that appeared to backfire.

In New Hampshire, former Democratic Gov. Jeanne Shaheen defeated Sununu in a rematch of their 2002 contest.

Democrats now exercise a slim 51-49 control of the chamber. Piggybacking on aggressive Barack Obama voter-registration and get-out-the-vote drives in battleground states, Democrats were reaching for a coveted 60-seat, filibuster-proof Senate majority. However, leaders in both parties portrayed that goal as a long shot.

In pair of western races, Reps. Tom and Mark Udall took over Senate seats held by retiring Republicans. Tom Udall, the son of former Interior Secretary Stewart Udall, defeated Republican Rep. Steve Pearce to succeed Pete Domenici in New Mexico. Tom’s cousin Mark, the son of the late Rep. Morris Udall of Arizona, won the Colorado seat held by Republican Wayne Allard, who did not seek re-election.

Democratic former Virginia Gov. Mark Warner breezed to victory to take a Virginia Senate seat long held for by terms by retiring GOP Sen. John Warner. Warner beat another former governor, Republican Jim Gilmore, in the race to replace retiring five-term Sen. John W. Warner. The two Warners are not related.

Democratic vice presidential candidate Joe Biden won another six-year term representing Delaware in the Senate. It became moot when Obama won the presidential election.

Senate Republican leader Mitch McConnell, who had been a target of national Democrats, won re-election against two-time Democratic gubernatorial candidate Bruce Lunsford in a contentious race.

With Warner’s victory in Virginia, Democrats now control both Senate seats and the governor’s mansion. Virginia usually votes Republican in presidential elections, but this year Democrats viewed it as one of their most promising pick ups.

Democrats were counting on a slumping economy, an unpopular war and voter fatigue after eight years of President Bush to bolster that majority, building on the six seats they added in 2006.

Reaching their goal of 60 seats was a stretch. But having a majority in the high 50s would enable Democrats to exercise far more control than they have now, since some Republicans probably would join them in efforts to break Senate logjams on many bills and judicial appointments.

Democrats’ hoped that only two Democratic senators would lose their Senate seats as a result of the national elections: Biden and Obama. Democratic governors in Illinois and Delaware are sure to appoint Democrats to replace them.

The Senate seats of Obama and GOP presidential candidate John McCain were not up this year.

Democrats had fewer seats to defend than Republicans. Of the 35 races on Tuesday’s ballot, 23 are now held by Republicans, 12 by Democrats.